1,4-dihydro-4-oxo-3-quinoline derivatives as selectively toxic mammalian antibacterial agents

ABSTRACT

Compounds of the formula ##STR1## and the pharmaceutically acceptable salts thereof, wherein Q, X and R are as defined below. The compounds of formula I are broad spectrum mammalian antibacterial agents and exhibit favorable selectivity against procaryotic cells.

BACKGROUND OF THE INVENTION

The present invention relates to new 1,4-dihydro-4-oxo-3-quinolinederivatives that are antibacterial agents suitable for the treatment ofbacterial and mycoplasma infections in mammals, including humans. Thecompounds of the invention exhibit unexpectedly favorable selectivityagainst procaryotic cells, as measured by their activity againstprocaryotic DNA gyrase versus mammalian topoisomerase II.

U.S. Pat. Nos. 4,775,668 and 4,861,779 refer to antibacterial compoundshaving the formula ##STR2## wherein R¹ is hydrogen, a pharmaceuticallyacceptable cation, or alkyl; A is CH, CF, CCl or N; Y is alkyl,haloalkyl, cyclopropyl, vinyl, methoxy, N-methylamino, p-flurophenyl,p-hydroxyphenyl or p-aminophenyl; or A is carbon and is taken togetherwith Y and the carbon and nitrogen to which A and Y are attached to forma five to seven membered ring which is optionally substituted; and R² isa bridged-diazabicycloalkyl group.

Derwent anonymous research disclosure no. 88-103269/15 refers tocompounds of the formula ##STR3## wherein R¹ is (C₁ -C₃)alkyl,cyclopropyl, vinyl, hydroxyethyl, fluoroethyl, methoxy, amino,methylamino, dimethylamino, ethylamino, phenyl, 4-fluorophenyl or2,4-difluorophenyl; R² is hydrogen, (C₁ -C₄)alkyl or5-methyl-2-oxo-1,3-dioxol-4-ylmethyl; R³ is methyl or one of elevencyclic amino groups wherein one of said eleven cyclic amino groups is##STR4## R⁴ is hydrogen, (C₁ -C₄) alkyl, hydroxyethyl, allyl, propargyl,CH₂ COCH₃, phenacyl, CHO, SCFCl₂, SO₂ CFCl₂, SCOOMe, benzyl,4-aminobenzyl or 5-methyl-2-oxo-1,3-dioxo-4-ylmethyl; R⁵ is hydrogen ormethyl; R⁶ is hydrogen, (C₁ -C₄) alkyl, phenyl or CH₂ OCH₂ Ph; R⁷ ishydrogen, amino, methylamino, ethylamino, aminomethyl,methylaminomethyl, ethylaminomethyl, dimethylaminomethyl, hydroxy orhydroxymethyl; R⁸ is methyl, ethyl or chloro; X is fluyoro, chloro ornitro; Y is hydrogen, fluoro or amino; A is nitrogen or CR⁹ ; and R⁹ ishydrogen, alkoxy, (C₁ -C₃)alkylthio, halogen, methyl or nitro; or R¹ andR⁹ are OCH₂ CH(Me), SCH₂ CH(Me), COCH₂ CH(Me) or CH₂ CH₂ CH(Me). Thisbroad generic disclosure includes several compounds of the presentinvention but does not teach or suggest their surprising and favorableselectivity as antibacterial agents against procaryotic versuseucaryotic cells.

SUMMARY OF THE INVENTION

The present invention relates to compounds of the formula ##STR5##wherein Q is methyl, ethyl, hydroxyethyl or hydrogen;

R is hydrogen, (C₁ -C₃) alkyl, benzyl, (C₁ -C₃) alkanoyloxymethyl, (C₁-C₃) alkanoyloxyethyl, benzoyloxymethyl, benzoyloxyethyl, or 5-[(C₁-C₃)alkyl]-2-oxo-1,3-dioxolen-4-ylmethyl; and

Y is cyclopropyl or substituted cyclopropyl, wherein said substitutedcyclopropyl is substituted with one to three substituents independentlyselected from the group consisting of (C₁ -C₃) alkyl, halo hydroxy, or(C₁ -C₃) alkoxy;

and the pharmaceutically acceptable salts and hydrates of suchcompounds.

As used herein, unless indicated otherwise, "halo" includes fluoro,chloro, bromo and iodo.

Examples of pharmaceutically acceptable salts of the compounds offormula I are the acid addition salts of acetic, lactic, succinic,maleic, tartaric, citric, gluconic, ascorbic, benzoic, methanesulfonic,cinnamic, fumaric, phosphoric, hydrochloric, hydrobromic, hydroiodic,and sulfonic acids, and the cationic salts of alkali metals such assodium or potassium, alkaline earth metals such as magnesium or calcium,ammonium, and organic amines such as diethanolamine andN-methylglucamine.

The term "pharmaceutically acceptable salts and hydrates", as usedherein, includes pharmaceutically acceptable salts, hydrates,pharmaceutically acceptable salts of hydrates, and hydrates of suchsalts.

The present invention also relates to a pharmaceutical compositioncomprising an antibacterially effective amount of a compound of theformula I, or a pharmaceutically acceptable salt thereof, and apharmaceutically acceptable carrier.

The present invention also relates to a method of treating a mammal,including a human, having a bacterial disease, which comprisesadministering to the mammal an antibacterially effective amount of acompound of the formula I, or a pharmaceutically acceptable saltthereof.

Compounds of the formula I wherein R is (C₁ -C₃) alkyl, benzyl, (C₁ -C₃)alkanoyloxymethyl, (C₁ -C₃) alkanoyloxyethyl, (C₁ -C₃) benzoyloxymethyl,(C₁ -C₃) benzoyloxyethyl or 5-[(C₁-C₃)alkyl]-2-oxo-1,3-dioxolen-4-ylmethyl, are prodrugs of compounds ofthe formula I wherein R is hydrogen.

The compounds of the formula I may have chiral centers and may exist inseveral stereoisomeric forms. This invention includes all stereoisomersof the compounds of formula I, and mixtures thereof.

Preferred compounds of the invention are1-cyclopropyl-6-fluoro-8-methoxy-7-(1S,4S)-5-methyl-2,5-diazabicyclo[2.2.1]hept-2-yl-1,4-dihydro-4-oxo-3-quinoline carboxylic acid and the pharmaceuticallyacceptable salts and hydrates thereof.

DETAILED DESCRIPTION OF THE INVENTION

Compounds of the formula I may be prepared as illustrated in thefollowing reaction scheme. ##STR6##

Referring to the above reaction scheme, compounds of the formula I,wherein Q is hydrogen and R and Y are as defined above, may be preparedby reacting a compound of the formula II, wherein R and Y are as definedabove and Hal is chloro, bromo, fluoro or iodo, with a compound of theformula III.

The reaction may be performed in the absence of a solvent or in thepresence of a polar, reaction inert solvent such as acetonitrile,tetrahydrofuran, ethanol, chloroform, dimethylformamide, pyridine, orwater, or mixtures thereof. The reaction is preferably carried out inthe presence of a base such as an alkali metal or alkaline earth metalcarbonate or bicarbonate, or a secondary or tertiary amine such astriethylamine, pyridine or picoline. The preferred reaction temperatureis from about 60° to about 100° C., but temperatures from about 10° toabout 150° C. are generally suitable.

The starting materials of formula II are known in the art, e.g. asdisclosed in European Patent Application 0230295A2.

Compounds of the formula III, wherein Q is hydrogen, may be made asdescribed in U.S. Pat. No. 3,947,445 and in J. Org. Chem., 31, 1059(1966).

Compounds of the formula I wherein Q is methyl may be prepared from thecorresponding compounds of the formula I wherein Q is hydrogen byconventional methylation procedurs. For example, one standardmethylation procedure known in the art involves the use of formic acidand paraformaldehyde. According to this procedure, a mixture of analkali or alkaline earth metal formate (preferably sodium formate),formic acid (preferably 87% formic acid), formalin (preferably 37%formalin), and a compound of the formula I wherein Q is hydrogen arereacted to yield a compound of the formula I wherein Q is methyl. Thereaction is typically carried out by stirring the reactants forapproximately 0.5 to 24 hours, preferably about 2 hours, at atemperature of from about 80° to about 150° C., preferably from 100° to120° C. The compounds of formula I so produced can be isolated byconventional purification techniques.

Compounds of the formula I wherein Q is ethyl or hydroxyethyl may beprepared by reacting a compound of the formula I wherein Q is hydrogenwith, respectively, ethyl iodide or 2-bromoethanol. This reaction isgenerally carried out in a reaction inert solvent such astetrahydrofuran (THF) or dimethylformamide (DMF), and in the presence ofan organic base such as triethylamine, at a temperature of from about50° to 150° C., preferably about 100° C., for approximately 24 hours.The compound of formula I so produced can be isolated by conventionalpurification techniques.

In each of the reactions described above, pressure is not critical.Pressures from about 0.5 to about 3 atmospheres are generally suitable,and ambient pressure is preferred as a matter of convenience.

The pharmaceutically acceptable acid addition salts of compounds theformula I may be prepared in a conventional manner by treating asolution or suspension of the free base of the formula I with about onechemical equivalent of a pharmaceutically acceptable acid. Conventionalconcentration and recrystallization techniques are employed in isolatingthe salts.

The pharmaceutically acceptable cationic salts of compounds of theformula I may be prepared by conventional methods from the correspondingacids, e.g. by reaction with about one equimolar amount of a base.

The novel compounds of the formula I and the pharmaceutically acceptableacid addition salts thereof are useful in the treatment of bacterialinfections of broad spectrum, particularly in the treatment ofgram-positive bacterial infections.

The compounds of the invention may be administered alone, but willgenerally be administered in admixture with a pharmaceutical carrierselected with regard to the intended route of administration andstandard pharmaceutical practice. For example, they can be administeredorally or in the form of tablets containing such excipients as starch orlactose, or in capsules either alone or in admixture with excipients, orin the form of elixirs or suspensions containing flavoring or coloringagents. In the case of animals, they are advantageously contained in ananimal feed or drinking water in a concentration of about 5 to about5000 ppm, preferably about 25 to about 500 ppm. They can be injectedparenterally, for example, intramuscularly, intravenously orsubcutaneously. For parenteral administration, they are best used in theform of a sterile aqueous solution which can contain other solutes, forexample, enough salt or glucose to make the solution isotonic. In thecase of animals, compounds can be administered intramuscularly orsubcutaneously at dosage levels of about 0.1 to about 50 mg/kg/day,preferably about 0.2 to about 10 mg/kg/day given in a single daily doseor up to 4 divided doses.

The compounds of the invention can be administered to humans for thetreatment of bacterial diseases by either the oral or parenteral routesand may be administered orally at dosage levels of about 0.1 to about500 mg/kg, advantageously about 0.5 to about 50 mg/kg/day given in asingle dose or up to 4 divided doses. For intramuscular or intravenousadministration, dosage levels are about 0.1 to about 200 mg/kg/day,preferably about 0.5 to about 50 mg/kg/day. While intramuscularlyadministration may be a single dose or up to 4 divided doses,intravenous administration can include a continuous drip. Variationswill necessarily occur depending on the weight and condition of thesubject being treated and the particular route of administration chosenas will be known to those skilled in the art.

The antibacterial activity of the compounds of the present invention maybe determined by testing according to the Steer's replicator techniques,which is a standard in vitro bacterial testing method described by E.Steers et al., Antibiotics and Chemotherapy, 9, 307 (1959). Theselective antibacterial activity of the compounds of the formula Iagainst procaryotic versus eucaryotic cells may be determined bycomparing their activity against procaryotic DNA-gyrase versus mammaliantopoisomerase II according to the procedure of Barrett et al.,Antimicrobial Agents and Chemotherapy, 33 (10) (October, 1989).

The following examples serve to illustrate but not limit the presentinvention.

EXAMPLE 1 a. Ethyl 3-methoxy-2,4,5-trifluorobenzoylacetate

Dianion of monoethylamalonate: To a solution of monoethylmalonic acid(9.8 g, 73 mmol) in anhydrous tetrahydrofuran (350 mL) at -78° C. wasadded n-butyllithium (50 mL, 80 mmol, 1.6 M, 1.1 equiv). The reactiontemperature was then raised to -5° C. and additional n-butyllithium wasadded (50 mL, 80 mmol, 1.6 M, 1.1 equiv. ) dropwise. The reactionmixture was allowed to stir for an additional hour at -5° C. and wasthen cooled to 78° C.

Addition of acid chloride: 3-Methoxy-2,4,5-trifluorobenzoyl chloride(6.38 g, 24 mmol), prepared from 3-methoxy-2,4,5-trifluorobenzoic acid(5.0 g, 24 mmol) and excess thionyl chloride at reflux for 2 hoursfollowed by removal of excess thionyl chloride in vacuo, was addeddropwise as a solution in anhydrous tetrahydrofuran (50 mL) to thedianion of monoethylmalonate at -78° C. The reaction mixture was allowedto warm to room temperature for 2 hours and was quenched by pouring into1N hydrochloric acid. The aqueous layer was extracted with diethyl ether(3×150 mL) and the combined organic layers were washed with saturatedaqueous sodium bicarbonate and water, dried over anhydrous magnesiumsulfate, filtered and concentrated in vacuo to afford 5.15 g, 76% yieldof a white solid after recrystallization from hexanes, m.p. 42°-44° C.

Anal.: Calcd. for C₁₂ H₁₁ F₃ O₄ : C, 52.20; H, 3.90. Found: C, 52.18; H,3.85.

MS (low resolution) M+=276.

b. Ethyl 2-(3-methoxy-2,4,5-triflurobenzoyl)-3-ethoxyacrylate

A mixture of ethyl-3-methoxy-2,4,5-trifluorobenzoylacetate (500 mg, 1.8mmol), ethyl orthoformate (0.45 mL, 2.72 mmol) and acetic anhydride (460mg, 4.5 mmol, 2.5 eq) was stirred at 110° C. for 12 hours and the excessreagents were removed by distillation under high vacuum (0.1 mmHg) togive 590 mg of a yellow-orange oil. This material was used directly inthe next step without further purification or characterization.

c. Ethyl 2-(3-methoxy-2,4,5-trifluorobenzoyl)-3-cyclopropylaminoacrylate

To a solution of ethyl2-(3-methoxy-2,4,5-triflurobenzoyl)-3-ethoxyacrylate (590 mg, 1.8 mmol)in methylene chloride (15 mL) at 0° C. was added a solution ofcyclopropylamine (114 mg, 1.98 mmol, 1.2 equiv) in methylene chloride (5mL). The reaction mixture was warmed to room temperature and allowed tostir for 2 hours. The solvent was removed in vacuo and the crudeconcentrate was purified by flash chromatography on silica gel(methylene chloride/ethyl acetate 50:1 v/v) to provide 438 mg, 62% yieldover two steps, of a viscous yellow oil.

d. Ethyl8-methoxy-1-cyclopropyl-6,7-difluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylate

To a solution of ethyl2-(3-methoxy-2,4,5-trifluorobenzoyl)-3-cyclopropylaminoacrylate (440 mg,1.29 mmol) in anhydrous tetrahydrofuran (15 mL) at 0° C. was addedsodium hydride (62 mg, 1.5 mmol, 1.1 equiv, 60% in mineral oil). Thereaction mixture was allowed to stir at 50° C. for 12 hours. The mixturewas cooled to room temperature and filtered. The mother liquor wasconcentrated and a white precipitate formed. The material was collectedby suction filtration and air-dried to give 312 mg, 75% yield of a purewhite solid, m.p. 178°-181° C.

e.1-Cyclopropyl-6,7-difluoro-8-methoxy-1,4-dihydro-4-oxo-3-quinolinecarboxylicacid

A mixture ofethyl-1-cyclopropyl-6,7-difluoro-8-methoxy-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid (500 mg, 1.55 mmol), glacial acetic acid (5 mL), and 1Nhydrochloric acid (1 mL) was allowed to reflux for 2 hours and waspoured into ice water. The resulting precipitate was collected bysuction filtration and washed with distilled water and diethyl ether togive 420 mg, 91% yield of a white solid, m.p. 187°-189° C.

f. 1-Cyclopropyl-6-fluoro-8-methoxy-7-[(1S:4S)-5-methyl-2,5-diazabicyclo[2.2.1]hept-2-yl]-1,4-dihydro-4-oxo-3-quinolinecarboxylicacid

A mixture of1-cyclopropyl-6,7-difluoro-8-methoxy-1,4-dihydro-4-oxo-3-quinolinecarboxylicacid (400 mg, 1.4 mmol),(1S:4S)-2-methyl-2,5-diazabicyclo-[2.2.1]heptane dihydrochloride (300mg, 1.63 mmol, 1.2 equiv) and 1,8-diazabicyclo[5.4.0]undec-7-ene (710mL, 4.75 mmol, 3.4 equiv) in anhydrous dimethyl sulfoxide (25 mL) washeated to 75° C. for 18 hours. The reaction mixture was cooled to roomtemperature and poured into distilled water adjusted to pH=7.4 withsaturated aqueous sodium bicarbonate. The aqueous phase was extractedseveral times with chloroform. The chloroform layer was then extractedwith 1N HCl and the acidic aqueous phase was back extracted withchloroform. The aqueous layer was adjusted to pH=7.4 with saturatedaqueous sodium bicarbonate and extracted with chloroform. The chloroformextracts were dried over sodium sulfate, filtered and concentrated invacuo to a dark oil which was purified by flash chromatography(chloroform/methanol 10:1 v/v) to give 65 mg, 12% yield of a whitesolid, m.p. 190°-212° C with decomposition.

Anal.: Calcd. for C₂₀ H₂₂ FN₃ O₄. 0.5H₂ O: C, 60.60; H, 5.80; N, 10.60.Found: C, 60.57; H, 5.70; N, 10.59.

I claim:
 1. A compound of the formula ##STR7## wherein Q is methyl, Y iscyclopropyl and R is hydrogen, or a pharmaceutically acceptable salt orhydrate of said compound.
 2. A pharmaceutical composition for treatingor preventing a bacterial disease in a mammal comprising anantibacterially effective amount of a compound according to claim 1 anda pharmaceutically acceptable carrier.
 3. A method of treating orpreventing a bacterial disease in a mammal, said method comprisingadministering to said mammal an antibacterially effective amount of acompound according to claim 1.